Field of Invention
The present invention relates to a high voltage battery for vehicles with improved cooling efficiency and, more specifically, to a battery system and a temperature controlling unit that reduces the number or size of battery packages, and remedy situation of a unit battery not providing required power to an electric vehicle due to high temperature or situation of the battery being exposed to temperature which may significantly impair the durability of the battery.
Description of Related Art
A battery is made of a module which is formed by stacking a plurality of thin plate cells, and a plurality of modules is connected together in series to form a battery package. In the battery pack, heat is produced during charging and discharging by a chemical reaction, and the charging and discharging capacity of the battery varies with the temperature of the cells. Thus, it is required to maintain the cell temperature within an appropriate range such that the inner temperature of the battery is maintained at predetermined temperatures, for example, 25 to 40 degrees, during operation.
Therefore, a system for removing heat generated from a high-voltage battery is indispensible for an electric-powered vehicle using such a battery. The cooling system of the electric-powered vehicle is classified into water-cooling and air-cooling systems, in which the air-cooling system is preferred in most cases, as the water-cooling system has drawbacks of a complicated structure and high cost in spite of good cooling efficiency.
In the air-cooling system, cooling efficiency varies with the structure of a cooling path, and the uniform distribution of cooling air is particularly important when the number of modules is increased for realizing an increase in the capacity of battery.
The most important factor when cooling the battery of an electric-powered vehicle will be the highest temperature of the battery and a temperature difference between unit battery cells. The highest temperature of the battery may be efficiently controlled by adjusting the amount of cooling air, and the temperature of inlet air. Although the temperature difference between battery cells may be reduced by improving the structure of the duct system to some extent, the temperature difference inevitably occurs between battery cells.
Although in an ideal case a reduction in the temperature difference between battery cells may be achieved by providing the same amount of cooling air to each cooling path between each unit cell, this solution cannot be realized in a real system. Thus, in actual systems, merely attempting to provide a uniform amount of cooling air to each cooling path is all that is possible, but such an approach has limitations.
Disregarding insignificant structural differences, most conventional cooling systems arrange battery cells linearly, and provide cooling air from a sirocco fan by using a duct system. Characteristics of the sirocco fan and duct system accordingly restrict the uniform distribution of cooling air. As a result, the uniform cooling of each battery cell is not achieved, thereby causing a temperature deviation between battery cells, e.g. 5° C., so a desired battery capability through the optimization of cell temperature cannot be secured.
An environmentally friendly vehicle equipped with a high-voltage battery should have a system for cooling the battery, and control the cooling system to prevent the battery from reaching an overheated state.
Conventional cooling of the high-voltage battery is achieved by drawing the interior air of the vehicle into the battery, and blowing this air into the space between each cell of the battery. As the above described system compulsorily blows air between cells, each flow path has a different flow resistance which deteriorates uniform cooling and makes flow noise. Additionally, the accumulation of foreign substances over time, such as dust, may cause serious problems.
If the cooling of the high-voltage battery is not sufficient, the battery may be overheated leading to deterioration of the battery, and in severe cases, may cause a safety problem such as a battery explosion. When the battery is charged or discharged, evaporation gas is generated in the electrolyte of the battery by electro-chemical reaction, and this gas may enter into the passenger compartment of the vehicle to cause a problem of air pollution in the compartment. Though, until now, there have been no restrictions regulating the interior air of the vehicle, an appropriate countermeasure is needed in anticipation of predicted legislation that will require regulating the interior air of electric vehicles.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.